Potato processors often make any number of different cuts to a potato during manufacturing of potato products, such as French fries and potato chips; each cut releases a small amount of starch. The cutting is usually done with some volume of water present to lubricate the cutting knives and drain away the starch. A processor can either choose to send this dilute potato starch water directly to a wastewater system or recover the potato starch. Recovery of the starch is desirable for two reasons: 1) starch companies compensate the manufacturer for the starch; 2) removing the starch from the waste water stream reduces the suspended solids and BOD loading which ultimately reduces the cost of treating that waste water.
Economics, specifically shipping cost, determine what kind of starch recovery system is used. For instance, the distance the manufacturer is from the starch company is often a determining factor as shipping excess water associated with starch cake or slurry is costly.
Current state of the art systems for recovering potato starch involve some or all of the following: 1) screening the dilute starch water, 2) pressurizing and flowing the water through a series of hydrocyclone separators to concentrate the starch, 3) forming a cake from the concentrated starch stream via a rotary vacuum filter and 4) drying that cake into a powder via a flash dryer.
The state of the art system designed to obtain starch slurry uses a screener and hydrocyclones. The state of the art system designed to obtain a starch cake uses a screener, hydrocyclones and a vacuum filter. Finally, the state of the art system designed to produce starch powder uses the screener, the hydrocyclones, vacuum filter and a flash dryer.
All three of the above mentioned systems require a great deal of piping, tanks, valves and various control equipment. Similar systems are used by other manufacturers, such as corn processors, to separate starch from the water used in their manufacturing processes.